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Seems like there are way too many Chris's. Chris Cervelli just recently did a 3.8L Turbo Mezger build for another local guy name Chris and now he is going to be doing an engine for T10Chris.
With that said, I was at the shop today with Chris Cervelli mapping out the next dyno session and what we are looking to accomplish. Johnny pulled the IDC1300x injectors yesterday and Chris had them flow tested just to be sure the were perfectly balanced for the rest of the tuning. The results came back today and they were all perfectly identical so we are good to go there. We are also going to pull the plugs to give them a quick visual to make sure all is good there. We have a little more tuning on the knock sensors and then Chris is going to tune the area below 4500rpm. On the last dyno session this past Wednesday we had the boost control inactive with the wastegates commanded open up to 4000. Combined with the super conservative timing, the area below 4000 rpm was very soft as can be seen on the dyno chart I posted above. We should be able to bring the area below 4500 by another 100hp or so once optimized. The goal is basically to make a nice even hp slope from 3000 rpm all the way to redline.
Last edited by powdrhound; 10-16-2022 at 12:36 AM.
Well, the Motec engine tuning is basically done. We spend another 3 hrs on the dyno on an unusually warm day which came in handy as it allowed us to really heat soak the engine. The dyno room ambient temp was 96F and the engine intake temp was right at 108-110F for all the pulls. This is about 10 degrees hotter that what we normally dyno at and is worth about 20-25whp that we gave up. Chris finalized the work on the knock sensing and also tweaked the timing and variocam profile. The engine is phenomenally smooth and pulls in a no-drama manner that is simply effortless. Chris really hit it out of the ball park with the level of detail that went into this. At this point, we basically do any final touchups to the file at the track.
Here is the result at 1.3 bar (19psi). It's simply mindbogling the amount of power this engine makes at such a low boost level.
The 1.3 bar file above is actually a bit too much to use at the track as traction would be an issue due to the large amount of torque, especially in the midrange. With 825 ft.lb wtq we are also slightly above the 750 ft.lb torque rating of the small Tilton 5.5" carbon clutch. As such, Chris reduced the boost level to 1.1 bar max with a sizable reduction to a max of 0.75 bar in the 4-4.5K range to get a much more user friendly track file.
This is the 1.1 bar (16psi) file that will be the default file for track use. This is very much a GT3 type power curve albeit slightly higher up in the graph.
Here is a good graph that clearly demonstrates the difference between the XR1000 and XR980 turbochargers, both at 1.3 bar boost. The only difference are the turbochargers and the larger exhaust headers used in conjunction with the XR1000s. We figure the headers are worth 40whp with the turbochargers making up the difference along with the substantially more precise tuning afforded by the M150 ECU. You can see that the XR980s have a small advantage below 3700rpm but above that it's not even a fair fight. It's also very interesting to note how much smoother the Motec curve is compared to the slightly jagged OEM ECU / Cobb curve.
One last thing to mention is the fact that we are still using the OEM Y-pipe and the OEM intake distributors. Although I do believe there is another 30-40 hp to be had with a larger Y-pipe, for most applications the OEM parts are quite adequate. We are going to fabricate a larger Y-pipe which will be retrofitted to validate the data. Cheers...
Last edited by powdrhound; 10-23-2022 at 05:14 AM.
Awesome power. Goes to show there's a lot to be had with at the least some port work on the headers and opening up the intake. I remember you boasting about still having stock parts in these places, but it's apparent that they were leaving power on the table, especially now with the turbos moving much more air. Are those IAT similar to what you see outside of the dyno?
Awesome power. Goes to show there's a lot to be had with at the least some port work on the headers and opening up the intake. I remember you boasting about still having stock parts in these places, but it's apparent that they were leaving power on the table, especially now with the turbos moving much more air. Are those IAT similar to what you see outside of the dyno?
Motec showed the ambient temp as 96F and the IAT as 108-110 on each pull. As more air would begin to flow through the engine at the start of the pull, the IAT would would initially drop to 104-105F before going up as power would build. So yes, there is a relatively modest 10 degree delta. This is after 32 pulls on the dyno over a 3 hour timeframe.
While we did not do anything on the intake side, although very good overall, I think the OEM headers do have their limits once you get past a certain output level. The 48mm headers were definitely a huge aid in eliminating the bottle neck at this point. Combined with the larger XR1000 turbine, we did see a substantial lowering of the turbine drive pressure data. It's hard to say what amount of benefit these headers would bring at a lower power level but in our estimation one would still see a 20-25whp benefit at a more modest 600wph. I am really looking forward to the results of a larger Y-pipe as the OEM piece has to be a restriction at this amount of flow.
Last edited by powdrhound; 10-22-2022 at 01:53 PM.
The beauty of full control, very nice graphs John.
Question though, do you see a scenario where you would us the 1.3 bar map?
The way we have the Motec system set up on the car makes it very easy to select a different map from the ECU simply by toggling available on the dash. I can see using the 1.3 file for a Time trial run if I needed the extra output for some reason. We could also do a 1.5 or 1.6 bar race gas file which would net closer to 1100 whp but I just don't see the benefit at the expense of the additional wear and tear. I think we will make another 1.3 bar file which would have the midrange tuned down so that it would mirror the 1.1 bar track map with the GT3 type curve but simply move that curve up another another 50-75whp or so.
We did the 1.3 bar file above simply to demonstrate what the turbochargers are mechanically capable of in the low to mid rpm range with the N75 set to 100% and set to start tapering at 4000rpm or so. As you can see they leave very little on the table compared to the 980s. With the 1.1 bar track file, we start tapering the N75 value down from 100% sooner to reduce the mid range torque peak. We use dual Motec N75 valves (one for each bank) so their range is a lot greater with an improved response time.
Great info re: Y-Pipe, I imagine a fair amount of parts are swapped out on mild 550-700 hp builds, where it appears it may not be enitrely necessary. You are still using the stock airbox and paper filter too right?
Great info re: Y-Pipe, I imagine a fair amount of parts are swapped out on mild 550-700 hp builds, where it appears it may not be enitrely necessary. You are still using the stock airbox and paper filter too right?
We are still using the OEM airbox, well, sort of. Chris installed air pressure sensors along several points in the intake path and that allowed us to evaluate restriction in the system. We have a sensor directly behind the filter in the location where the MAF sensor used to reside, another in front of the turbocharger inlet, one in the Y-pipe and another behind the throttle body in the plenum. At the level of airflow were are operating at, the OEM airbox provides a 100mb pressure drop at full boost which is relatively significant. The RUF plenum (post airbox) along with the large 2.75" plastic inlet pipes going to the turbo inlets only provide a 35mb pressure drop which indicates that the large intake pipes are very efficient. I was initially planning to install the 997TT/GT2 airbox with the silicone pipes but after looking closely at that design we realized that would have been a step backwards so we kept what we had in place.
The only thing to resolve on the intake was the pressure drop on the airbox. We are still using the OEM airbox but the top of the backside of the airbox is open across the top to allow air over the top of the whole filter panel. We switched to an BMC filter for better flow from the OEM filter and that helped. I do not have the pressure drop numbers handy but running on the dyno without the backside of the airbox installed showed a significant improvement . Although not on my car, this is a picture of the set up. Manthey Racing used this on their 996 turbo and GT3 race cars.
Would this really be necessary on a car with 700whp? Not likely as we did not see a problem with my previous set up using an unmodified OEM airbox and filter. It appears however based on looking at data that it does become limiting past the mid 700hp level.
...the top of the backside of the airbox is open across the top to allow air over the top of the whole filter panel. We switched to an BMC filter for better flow from the OEM filter and that helped....this is a picture of the set up. Manthey Racing used this on their 996 turbo and GT3 race cars.
Cool setup! Seems like the tricky part would be fabricating the additional external-air-intake portion on the engine lid! Or are they still available from Manthey?
Cool setup! Seems like the tricky part would be fabricating the additional external-air-intake portion on the engine lid! Or are they still available from Manthey?
I’m not sure if this would do much on a 996TT decklid Paul. The decklid I use has the ram air intakes similar to those on a GT2. That goes to a compartment in the decklid which has the opening on the right side for the airbox. That can be opened up to feed the airbox across the top with the long oval duct. That whole compartment is slightly pressurized with the ram air effect which in turn provides positive pressure to the airbox as the car is moving. Not sure if Manthey still makes these but they are available from my friend Markus.
10-15-2022, 01:44 AM
Chris Cervelli just recently did a 3.8L Turbo Mezger build for another local guy name Chris and now he is going to be doing an engine for T10Chris. 
